Qualities of an image (hereinafter referred to as image qualities) of an image forming apparatus include graininess, in-plane uniformity, character quality, and color reproducibility (including color stability). Today, when multi-color image forming apparatuses have become popular, it is sometimes said that the most important image quality is color reproducibility.
Humans have memories relating to expected colors (especially human skins, blue skies, metals, and the like) based on experience, and when the respective allowable ranges of the colors are exceeded, the colors feel strange. These colors are called memory colors, and the reproducibility thereof is now often required when a photograph or the like is output.
Not only in photographic images but also in document images, there are increasing demands for the color reproducibility (including stability) of an image forming apparatus from those such as office users who feel a difference from a color displayed on a monitor to be strange and graphic art users whose pursue color reproducibility in CG images.
Therefore, in order to meet the demands for color reproducibility from the users, an image forming apparatus has been proposed that reads an image whose color is to be measured formed on recording paper using a color sensor provided along a carrying path for the recording paper (for example, refer to PTL 1).
In this image forming apparatus, the image whose color is to be measured is formed on the recording paper using toner and feedback is provided for processing conditions such as light exposure and developing bias on the basis of a result of the reading, by the color sensor, of the image whose color is to be measured, in order to make it possible to reproduce a certain density, tone, and color.